On lun., oct. 02, 2023 at 15:46, Miquel Raynal <miquel.ray...@bootlin.com>
wrote:
> At some point when trying to use USB gadgets, two situations may arise
> and lead to a failure. Either the UDC (USB Device Controller) is not
> available at all (not described or not probed) or the UDC is already in
> use. For instance, as the USB Ethernet gadget remains bound to the UDC,
> the use of any other USB gadget (fastboot, dfu, etc) *after* will always
> fail with the "couldn't find an available UDC" error.
>
> Let's give a more helpful message by making a difference between the two
> cases. Let's also hint people who would get this error and grep it into
> the sources a better explanation of what's wrong with their workflow.
>
> Signed-off-by: Miquel Raynal <miquel.ray...@bootlin.com>
Reviewed-by: Mattijs Korpershoek <mkorpersh...@baylibre.com>
> ---
> While doing this I really wanted to add "much more" error comments but I
> faced another reality: often the messages are there but use
> pr_err/log_err which is actually silenced by default with LOGLEVEL=3, so
> I consider this unnecessary, as decreasing the loglevel will make these
> messages appear. I would have expected errors to be displayed, but I
> understand it makes the binaries even bigger.
>
> Resend: no change.
>
> Changes in v2:
> * s/UDC/UDCs/. I kept the sentence as it was as the suggested form did
> not sound well at all when there is only one UDC.
> ---
> drivers/usb/gadget/udc/udc-core.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/udc/udc-core.c
> b/drivers/usb/gadget/udc/udc-core.c
> index 7f73926cb3e..8405b03462e 100644
> --- a/drivers/usb/gadget/udc/udc-core.c
> +++ b/drivers/usb/gadget/udc/udc-core.c
> @@ -323,6 +323,7 @@ err1:
> int usb_gadget_probe_driver(struct usb_gadget_driver *driver)
> {
> struct usb_udc *udc = NULL;
> + unsigned int udc_count = 0;
> int ret;
>
> if (!driver || !driver->bind || !driver->setup)
> @@ -330,12 +331,22 @@ int usb_gadget_probe_driver(struct usb_gadget_driver
> *driver)
>
> mutex_lock(&udc_lock);
> list_for_each_entry(udc, &udc_list, list) {
> + udc_count++;
> +
> /* For now we take the first one */
> if (!udc->driver)
> goto found;
> }
>
> - printf("couldn't find an available UDC\n");
> + if (!udc_count)
> + printf("No UDC available in the system\n");
> + else
> + /* When this happens, users should 'unbind <class> <index>'
> + * using the output of 'dm tree' and looking at the line right
> + * after the USB peripheral/device controller.
> + */
> + printf("All UDCs in use (%d available), use the unbind
> command\n",
> + udc_count);
> mutex_unlock(&udc_lock);
> return -ENODEV;
> found:
> --
> 2.34.1
